Age at first birth and melanoma risk: a meta-analysis.

Age at first birth has been shown to be correlated with melanoma risk, but the results were inconsistent. Thus, a meta-analysis was undertaken to evaluate the relationship between age at first birth and melanoma risk. Studies published up to September 6, 2014 were identified through searches of PubMed and EMBASE databases. Random-effect model was used to pool the study-specific risk estimates (RRs) with 95% confidence intervals (CIs). Three case-control, three nested case-control, and five cohort studies were found to be eligible. In a comparison of the oldest versus youngest age at first birth, the pooled RR for melanoma risk was 1.47 (95% CI: 1.07-2.02) in all studies, 1.37 (95% CI: 0.47-4.02) in population-based case-control studies, 2.69 (95% CI: 1.56-4.64) in hospital case-control studies, 1.38 (95% CI: 0.66-2.88) in nested case-control studies, and 1.39 (95% CI: 0.89-2.17) in cohort studies. In the subgroup analysis according to sites where studies were performed, the pooled RR was 1.44 (95% CI: 0.99-2.08), 1.18 (95% CI: 0.30-4.60), and 2.36 (95% CI: 1.42-3.93) for Europe, Americas, and Australia, respectively. In the subgroup stratified by whether the included study provided adjustment for specific potential confounders or important risk factors, the relationship between age at first birth and melanoma risk was significantly modified by age, naevi/pigmentation, sunlight exposure, and hair colour. This meta-analysis based on available observational data reveals that age at first birth is positively associated with melanoma risk. However, this finding should be interpreted cautiously, as residual confounding cannot be excluded. More investigations with well-designed are warranted to extend this finding.